Effect of fertilization levels, age and canopy height of Lycopersicon hirsutum on the resistance to Myzus persicae

The effects of different levels of fertilization with nitrogen and potassium (NK), height within the canopy and plant age of Lycopersicon hirsutum f. glabratum (PI 134417) C. H. Mull and L. esculentum on the density of foliar cristalliferous idioblasts and trichomes, and on the levels of 2- tridecanone (2-TD) and 2-undecanone (2-UD) and their influence on the resistance to Myzus persicae (Sulzer) were investigated. NK levels were inversely related to densities of trichomes and cristalliferous idioblasts in L. esculentum, but only to densities of cristalliferous idioblasts in L. hirsutum. Trichome density increased with increasing height within the canopy and with plant age in L. esculentum and L. hirsutum. Density of cristalliferous idioblasts in L. hirsutum increased with canopy height reaching a maximum at mid-height within the canopy in opposition to L. esculentum in which a small decrease in density with height within the canopy was found. There was also a small decrease of idioblast density with increasing plant age for L. esculentum, while a greater and opposite variation took place in L. hirsutum. L. esculentum has mainly non- glandular leaf trichomes (90%), while L. hirsutum has mainly glandular trichomes (97%). The main glandular trichomes of L. hirsutum are producers of 2-TD and 2-UD, whose leaf content increases with increase of trichome density. A negative effect of 2-TD concentration and cristalliferous idioblast density on the survival and longevity of M. persicae was observed. Since L. hirsutum presented much higher levels of 2-TD and cristalliferous idioblast density than L. esculentum, L. hirsutum seems a promising source of resistance to M. persicae for tomato breeding programs.     

Role of canopy height in the resistance of Lycopersicon hirsutum f. glabratum to Tuta absoluta (Lep., Gelechiidae)

The objective of this work was to study the effect of plant canopy height on the resistance of the tomato species Lycopersicon hirsutum to the tomato leafminer Tuta absoluta . Determination of the levels of tridecan-2-one (2-TD) and undecan-2-one (2-UD) in L. hirsutum , as well as the leaf area, density and types of trichomes present in L. hirsutum and L. esculentum were made on apical, medium and basal parts of plant canopy. Correlation of these data were made with the following biological characteristics of T. absoluta : rates of oviposition and egg hatching; length of egg, larval and pupal stages; mortality of the larval and pupal stages; pupal weight; and sex ratio. Levels of 2-TD on leaves of L. hirsutum increased from bottom to top of canopy. Tuta absoluta had higher oviposition and egg hatching, as well as lower mortalities and smaller larval and pupal periods in L. esculentum than in L. hirsutum . Longer pupal period and greater number of small and large mines of T. absoluta were verified in the apical and medium parts of L. hirsutum plants. On the other hand, higher pupal mortality and longer larval periods were obtained in the apical and basal parts of the L. hirsutum plants. Larval mortality was higher in the basal part of those plants. In L. esculentum , leaves from the apical part of the plant promoted lower mortality, longer larval period and greater number of large mines of T. absoluta . However, a shorter pupal period was verified on leaves of the basal part. It appears that an increase in glandular trichome density in L. hirsutum leads to an increase in the levels of 2-TD, which, in turn slows down larval development.     

Resistance of wild Lycopersicon species to the potato moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae)

Abstract  Trichome-based host plant resistance of Lycopersicon species to potato moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), was examined in a laboratory bioassay. Neonate P. operculella were placed on the foliage of accessions of L. hirsutum , L. hirsutum f. glabratum , L. pennellii , L. cheesmanii f. minor and L. esculentum for 48 h . At the end of this period, larval mortality, the numbers of larvae emigrating from, and mining into, the leaf surface were recorded as were leaf area and the densities of trichomes. Analysis by categorical logistic regression found accessions differed in levels of resistance to P. operculella ( P  < 0.001). Further analysis using generalised linear models showed mortality was associated with high densities of type VI and low densities of type V trichomes; emigration from the leaf was associated with high densities of type I and type VII trichomes; and the numbers of mines associated with low densities of type I and type VI trichomes and increased leaf area. Although results indicate that certain accessions of L. hirsutum and L. hirsutum f. glabratum may be most appropriate for inclusion in a breeding program aimed at introducing trichome-based host plant resistance of wild Lycopersicon species into the tomato, further research is necessary to fully understand the mechanisms.     

Trichomes of Lycopersicon spp. and their effect on Myzus persicae (Sulzer) (Hemiptera: Aphididae)

Abstract The green peach aphid ( Myzus persicae ) is becoming resistant to many of the pesticides used in the tomato ( Lycopersicon esculentum ) industry. A potential alternative method of control is host-plant resistance, which may be mediated by trichomes. Resistance to the green peach aphid was assessed for six accessions of L. hirsutum, three of L. pennellii and a L. esculentum control. Mortality, entrapment and number of aphids unaffected by trichomes were recorded 24, 48 and 72 h after placement. Using multiple regression against counts of glandular and non-glandular trichomes, the role of foliar pubescence in resistance to the aphid was established. Lycopersicon pennellii possessed the highest level of resistance after 72 h and type IV trichome density accounted for 26.5% of variance in mortality ( P  < 0.001). Low densities of type IV and high densities of type VII trichomes increased the number of aphids 'unaffected' by trichomes, a relationship accounting for 29% of variance ( P  < 0.001). Information on which types of trichomes most strongly affect resistance to insect pests will aid future breeding and L. pennellii shows potential for use in breeding programs to increase levels of host-plant resistance in L. esculentum.     

Variation in Response of Wild Lycopersicon and Solanum spp. against Tomato Powdery Mildew (Oidium lycopersici)

A set of 154 accessions of nine wild Lycopersicon spp. and five accessions of three closely related Solanum spp. were tested for resistance to tomato powdery mildew ( Oidium lycopersici ). Screening revealed valuable sources of resistance, mainly among L. hirsutum, L. pennellii, L. cheesmanii, L. chilense, L. peruvianum and L. parviflorum. L. esculentum (all ssp.) and L. pimpinellifolium expressed high susceptibility to O. lycopersici inoculation. Results of variance and cluster analysis of responses to O. lycopersici coincide with recent taxonomic classification and genetic relationships within genus Lycopersicon .     

R2R3 MYB‐dependent auxin signalling regulates trichome formation,and increased trichome density confers spider mite tolerance on tomato

Unicellular and multicellular tomato trichomes function as mechanical and chemical barriers against herbivores. Auxin treatment increased the formation of II, V and VI type trichomes in tomato leaves. The auxin response factor gene SlARF4, which was highly expressed in II, V and VI type trichomes, positively regulated the auxin‐induced formation of II, V and VI type trichomes in the tomato leaves. SlARF4 overexpression plants with high densities of these trichomes exhibited tolerance to spider mites. Two R2R3 MYB genes, SlTHM1 and SlMYB52, were directly targeted and inhibited by SlARF4. SlTHM1 was specifically expressed in II and VI type trichomes and negatively regulated the auxin‐induced formation of II and VI type trichomes in the tomato leaves. SlTHM1 down‐regulation plants with high densities of II and VI type trichomes also showed tolerance to spider mites. SlMYB52 was specifically expressed in V type trichomes and negatively regulated the auxin‐induced formation of V type trichome in the tomato leaves. The regulation of SlARF4 on the formation of II, V and VI type trichomes depended on SlTHM1 and SlMYB52, which directly targeted cyclin gene SlCycB2 and increased its expression. In conclusion, our data indicates that the R2R3 MYB‐dependent auxin signalling pathway regulates the formation of II, V and VI type trichomes in tomato leaves. Our study provides an effective method for improving the tolerance of tomato to spider mites.     

Toxicity of methyl ketones from tomato trichomes to Tetranychus urticae Koch

The two methyl ketones, 2-tridecanone and 2-undecanone, are constituents of type VI glandular trichomes of the wild tomato, Lycopersicon hirsutum f. glabratum (PI 134417). They are known to cause mortality in several herbivorous insect species. In this study we investigated the effects of these chemicals on two strains of the two-spotted spider mite, Tetranychus urticae Koch, collected from tomato and cucumber crops in Dutch greenhouses. The two ketones were tested separately, in combination in the ratio found in L. hirsutum f. glabratum and in several other ratios to detect any synergistic interaction between them. We measured both the direct contact and residual toxicity, as well as the viability of the eggs produced by ketone-treated females. The methyl ketones can be considered as quite toxic to spider mites because their LC50 values were comparable to that found for the formulated acaricide amitraz. 2-Tridecanone was slightly more toxic than 2-undecanone but only in the tomato strain. Synergistic effects were not detected. In the bio assays for the residual effects of the two methyl ketones no significant mortality occurred but the mites avoided feeding on the treated surface and the eggs were laid almost exclusively on the untreated area. Furthermore, there was no significant egg viability for most of the treatments and when some egg viability occurred, it was not correlated to the dose of the chemical. Based on published data on the levels of methyl ketones in the trichome tips of wild and cultivated tomato (L. hirsutum f. glabratum and Lycopersicon esculentum Mill, respectively) it was calculated how many contacts are required to reach the LD50 (ng a.i. per mite). It appeared that on wild tomato just a few contacts suffice, but many are needed on cultivated tomato. Nevertheless, it seems justified to conclude that even in cultivated tomato, 2-tridecanone represents a naturally occurring acaricide. The cucumber and tomato strains of the two-spotted spider mite did not differ in their response to the methyl ketones. Because this is surprising, given the selection pressures on their respective host plants, we formulated two hypotheses, one explaining the absence of a difference due to cross-resistance and another one proposing that bioaccumulation obscures the underlying differences between the strains. This revised version was published online in November 2006 with corrections to the Cover Date.     

Genome-wide dissection of<Emphasis Type="Italic"> Fusarium</Emphasis> resistance in tomato reveals multiple complex loci

Resistance to different pathogenic races of Fusarium oxysporum f. sp. lycopersici (F. o. lycopersici) was explored at two genomic levels in tomato. Six independent Fusarium resistance loci were identified by comparing the responses of a complete set of 53 lines carrying different introgressed regions of the Lycopersicon pennellii genome in a L. esculentum background. The loci confer varying degrees of resistance to different races of the pathogen. Corresponding map positions from different tomato species were aligned and in some cases revealed parallel resistance to F. o. lycopersici with qualitative changes in race specificities. One of the loci identified corresponds to the previously characterized complex resistance locus I2, which is involved in resistance to F. o. lycopersici race 2. A novel member of this locus, I2C-5, which belongs to the NBS-LRR family of resistance genes, was cloned and shown to confer partial resistance in transgenic plants. Thus, at a particular complex locus gene members can confer full or partial resistance to F. o. lycopersici race 2. The results of our whole-genome mapping analysis underline the robust independent origin of resistance to a particular disease and demonstrate the conservation of resistance features at syntenic loci, together with the rapid diversification of genes for innate resistance within loci.     

Inhibition of Telenomus sphingis an egg parasitoid of Manduca spp. by trichome/2-tridecanone-based host plant resistance in tomato

The resistance of accession PI 134417 of the wild tomato Lycopersicon hirsutum f. glabratum C. H. Mull to Manduca sexta (L.) (Lepidoptera: Spingidae) and Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) is conditioned by the high densities of 2-tridecanone-containing, glandular trichomes associated with the foliage. In laboratory experiments, rates of parasitism of M. sexta eggs by Telenomus sphingis (Ashmead) (Hymenoptera: Scelionidae) were lower among eggs on PI 134417 foliage than among eggs on foliage of the cultivated tomato L. esculentum Mill. (cv. Better Boy). The latter is characterized by a significantly lower density of type VI glandular trichomes than PI 134417 and an absence of 2-tridecanone. Parasitism by T. sphingis was also reduced among eggs on foliage of the F₁ hybrid between PI 134417 and L. esculentum. The hybrid foliage lacks 2-tridecanone but has a density of type VI glandular trichomes that is intermediate between those of PI 134417 and L. esculentum, indicating that elevated densities of type VI glandular trichomes adversely affect T. sphingis. This conclusion was further substantiated by the finding that there were no differences among plant lines in the levels of parasitism of M. sexta eggs when the eggs were on foliage that had been divested of glandular trichomes.In bioassays in which T. sphingis adults or immatures in host eggs were exposed to filter paper treated with 2-tridecanone at rates comparable to those associated with PI 134417 foliage, 2-tridecanone was acutely toxic and caused high levels of mortality. In addition, at high concentrations, 2-tridecanone vapors were repellent to T. sphingis adults. However, when exposed to PI 134417 foliage, few T. sphingis adults were killed.Parasitism of M. sexta eggs was unaffected when the eggs were deposited by moths reared as fifth instar larvae on diet containing 2-tridecanone and/or 2-undecanone at levels comparable to those associated with PI 134417 foliage.     

Sesquiterpene carboxylic acids from a wild tomato species affect larval feeding behavior and survival of Helicoverpa zea and Spodoptera exigua (Lepidoptera: Noctuidae).

The sesquiterpene carboxylic acids (SCA), (+)-(E)-alpha-santalen-12-oic, (-)-(E)-endo-alpha-bergamoten-12-oic, and (+)-(E)-endo-beta-bergamoten-12-oic acid, are produced in glandular trichomes of Lycopersicon hirsutum f. typicum Humb. & Bonpl. accession (LA) 1777, which is highly resistant to a range of pests of cultivated tomatoes. L. esculentum Mill. Exposure of the larvae of two key tomato pests, tomato fruitworm [Helicoverpa zea (Boddie)] and beet armyworm [Spodoptera exigua (Hübner)], to these compounds in diets and on leaf surfaces resulted in reduced development rates and survival and deterred feeding. These effects were observed when levels of SCA, in artificial insect diet, applied to leaflets of susceptible cultivars, or synthesized in trichomes of leaves of plants, exceeded 2 mg SCA/g of diet or fresh leaf weight. This study suggests that cultivated tomatoes capable of synthesizing SCA, at 2 mg SCA/g of leaf tissue or greater, on their leaves and fruit would display enhanced host plant resistance to H. zea and S. exigua and other insect pests.     

Effect of plant variety, plant age and photoperiod on glandular pubescence and host-plant resistance to potato moth (Phthorimaea operculella) in Lycopersicon spp.

The effect of plant age and daylength on glandular pubescence was determined for two lines of tomato derived from Lycopersicon hirsutum (BTN 979 and LA 1777A) and a variety of L. esculentum (N 91‐1‐1‐1‐1). Densities of type I, IV, VI and VII glandular trichomes were lowest in N 91‐1‐1‐1‐1 and, over all varieties, were more dense on plants aged greater than 6 wk. Daylength interacted with variety to significantly affect densities of type VII trichomes only. Host‐plant resistance to Phthorimaea operculella was determined in preliminary tests using insects cultured from founders from a potato crop and in confirmatory tests using (less readily available) insects recovered from foliage of a tomato crop. Mortality of ex‐potato neonates on LA 1777 A and BTN 979 foliage was higher 18 h after placement than for N 91‐1‐1‐1‐1, with no effect of day length or plant age. Mortality for ex‐tomato neonates followed a similar trend. Ten days later, two‐thirds of ex‐tomato larvae had established mines on N 91‐1‐1‐1‐1 but fewer (16.7%) were live on other varieties. Stepwise multiple regression using variety as the sole factor was significant (P<0.001) in accounting for 61.4% of the variation in ex‐tomato larval survival but addition of other factors to the regression model was not significant. BTN 979 supported fewer, smaller adults to develop than did N 91‐1‐1‐1‐1, whilst no adults developed on LA 1777 A. In a non‐choice test using ex‐potato adults, significantly more eggs were laid on N 91‐1‐1‐1‐1 than on L. hirsutum varieties and 9‐wk‐old plants were preferred over plants three weeks older or younger. The same variety and plant age trends were evident in a free‐choice test using ex‐tomato adults.     

QTL analysis of quantitative resistance to Phytophthora infestans (late blight) in tomato and comparisons with potato.

Quantitative trait loci (QTLs) for resistance to Phytophthora infestans (late blight) were mapped in tomato. Reciprocal backcross populations derived from cultivated Lycopersicon esculentum x wild Lycopersicon hirsutum (BC-E, backcross to L. esculentum; BC-H, backcross to L. hirsutum) were phenotyped in three types of replicated disease assays (detached-leaflet, whole-plant, and field). Linkage maps were constructed for each BC population with RFLPs. Resistance QTLs were identified on all 12 tomato chromosomes using composite interval mapping. Six QTLs in BC-E (lb1a, lb2a, lb3, lb4, lb5b, and lb11b) and two QTLs in BC-H (lb5ab and lb6ab) were most consistently detected in replicated experiments or across assay methods. Lycopersicon hirsutum alleles conferred resistance at all QTLs except lb2a. Resistance QTLs coincided with QTLs for inoculum droplet dispersal on leaves, a trait in L. hirsutum that may contribute to resistance, and dispersal was mainly associated with leaf resistance. Some P. infestans resistance QTLs detected in tomato coincided with chromosomal locations of previously mapped R genes and QTLs for resistance to P. infestans in potato, suggesting functional conservation of resistance within the Solanaceae.     

Host plant resistance among tomato accessions to the spider mite <Emphasis Type="Italic">Tetranychus evansi</Emphasis> in Kenya

The spider mite Tetranychus evansi has a broad range of host plants. Control of T. evansi has been a big challenge to tomato farmers due to its fast rate of reproduction, development of resistance to chemical pesticides and its ability to use weeds as alternative hosts when the tomato plants are not available. The aim of the current study was to determine the host plant acceptance and the relative contributions of trichomes in the control of the red spider mite by comparing the survival, development and oviposition rates of the red spider mite on eight tomato accessions. Leaflets from eight tomato varieties were assayed with the spider mites to determine the egg laying capacity and developmental time of the spider mites on the tomato accessions as well as the trichome densities. Densities of trichome types I, IV, V and VI varied among the tomato accessions. Variation in types I, IV and VI accounted for most of the variation in mite responses. The varieties with high densities of types IV and VI had the highest fecundity and mite development did not go beyond the larval stage. The developmental time varied significantly among the tomato accessions. The results indicated that the higher the density of trichome type I the lower the adult survival. The findings indicated possible resistance of some of the tested tomato accessions against T. evansi which is partially associated with trichomes types and density.     

Genetic transfer of a twospotted spider mite (Acari: Tetranychidae) repellent in tomato hybrids

Lycopersicon hirsutum Dunal is very resistant to arthropod herbivory, and research on causes of resistance has often implicated trichomes and their secretions. To better understand relationships among resistance, repellency, and 2,3-dihydrofarnesoic acid, a trichome-borne sesquiterpenoid spider mite repellent, two tomato, Lycopersicon esculentum Miller, varieties were interbred with a highly resistant, spider mite repellent accession (LA1363) of L. hirsutum. Backcross and F2 generations were produced with each tomato variety. Whole leaves of 99 hybrids were bioassayed with twospotted spider mites, Tetranychus urticae Koch, allowing selection of six hybrids (two susceptible and four resistant) for each generation of each family. When these 24 hybrids were characterized for spider mite repellency with thumbtack bioassays, two hybrids had repellent leaflets, demonstrating that repellency was genetically transferred to interspecific tomato hybrids. Leaflet washes containing trichome secretions from each of three hybrids, including the two having repellent leaflets, were repellent in bridge bioassays. For the two hybrids having repellent leaflets and leaflet washes, removal of trichome secretions by dipping leaflets in methanol eliminated leaflet repellency. 2,3-Dihydrofarnesoic acid was present in trichome secretions of the hybrids having leaflet repellency, and it also was present in secretions of other hybrids, indicating that its presence is essential, but not sufficient for leaflet repellency. With regard to resistance, 16 of the hybrids tested had been identified as resistant in a whole leaf bioassay, but only two had repellent leaflets, indicating that other mechanisms of resistance are present in the resistant L. hirsutum parent.     

Interaction of fertilizer regime with host-plant resistance in tomato

The effect of fertilizer regime on trichome- and lamellar-based resistance in the wild tomato species, Lycopersicon hirsutum f. glabratum C.H. Mull accession PI 134417, to three insect pests of tomato, the tobacco hornworm, Manduca sexta (L.), the colorado potato beetle, Leptinotarsa decemlineata (Say), and the tomato fruitworm, Heliocoverpa zea (Boddie), was examined. Increasing the rate at which NPK fertilizer was applied, from 1.8 to 19.6 g/plant/week, reduced the trichome-based resistance of PI 134417 to M. sexta and L. decemlineata by lowering both the density of type VI (sensu Luckwill, 1943) glandular trichomes and the amount of 2-tridecanone contained in the tips of these trichomes. 2-Tridecanone is a toxic methyl-ketone responsible for glandular trichome-mediated resistance in PI 134417 to M. sexta and L. decemlineata. A similar increase in the application rate of NPK fertilizer reduced the lamellarbased resistance of PI 134417 to L. decemlineata and H. zea. The meachanisms for this reduction of resistance are unknown, but may be related to improved nutritional quality of hosts at higher fertilizer regimes.     

Foliar pubescence and resistance to potato moth, Phthorimaea operculella, in Lycopersicon hirsutum

Pubescence characteristics for six accessions of Lycopersicon hirsutum Dunal and five accessions of L. hirsutum f. glabratum CH Mull. were determined and compared with those of an accession of cultivated tomato (L. esculentum Mill.). Removal of trichome exudates from excised leaflets using ethanol solution resulted in a reduced mortality and increased survival of potato moth (Phthorimaea operculella (Zeller)) neonates for the accessions that were most lethal when not treated with ethanol solution. No such treatment effect was evident for L. esculentum or for the L. hirsutum accession with least effect on neonates when its trichomes were intact. In a glasshouse experiment with caged intact plants, mortality of neonate P. operculella placed on the abaxial surface was greater on seven accessions than for L. esculentum.Neonates were less severely affected on the adaxial surface. Eleven days after inoculation, no live larvae were found on LA 1927, PI 127827, PI 134418, and PI 134428, and numbers on other accessions were lower than for L. esculentum. Eventual emergence of adults followed a similar trend. Multiple regression of insect data against pubescence indicated a significant correlation between density of type IV and VI trichomes and neonate mortality, decreased larval development and decreased adult emergence. Non-glandular type V trichomes were positively correlated with high survival of insects to 11 days and to adult. Though factors other than glandular trichomes are likely to be important, increased density of type IV and VI, along with reduced type V, are shown to be important to select in breeding for P. operculella resistance.     

日本刀角瓢虫对不同番茄品种的产卵选择性及其影响因素

【目的】明确日本刀角瓢虫Serangium japonicum对叶毛密度和类型不同的番茄Lycopersiconesculentum品种的产卵选择性。【方法】以4个番茄品种(砧木101、闽粉樱1号、砧木301和以色列超级金刚)作为日本刀角瓢虫的寄主植物,观察番茄叶片背面超微结构,统计叶片背面叶毛类型及密度;用叶蝶法和植株法测定日本刀角瓢虫雌成虫在带烟粉虱Bemisia tabaci卵的4个番茄品种上的产卵量占比;并测定日本刀角瓢虫在这4个番茄品种叶片上的子代及成虫表现(生长发育、繁殖和捕食能力)以及对叶片的附着力,雌成虫对4个番茄品种健康叶片和受烟粉虱为害叶片的气味选择以及4个番茄品种叶碟和植株上日本刀角瓢虫卵被同类捕食的风险。【结果】4个番茄品种叶片背面叶毛类型均具有非腺毛和腺毛,其中,非腺毛有Ⅱ, Ⅲ和Ⅴ型,腺毛有Ⅰ, Ⅳ Ⅵ和Ⅶ型,且均以Ⅴ型非腺毛密度最高。以色列超级金刚叶片背面的叶毛密度显著低于其他3个供试番茄品种。日本刀角瓢虫偏好在以色列超级金刚上产卵,在以色列超级金刚、砧木101和闽粉樱1号上的繁殖力(165~223.92粒/雌)显著高于在砧木301上的(2809粒/雌)。日本刀角瓢虫子代由卵发育至成虫的历期在闽粉樱1号上最短(15.73 d),在砧木101上最长(23.00 d)。日本刀角瓢虫在4个番茄品种上的产卵选择性与子代表现及亲代表现无显著相关性,而与日本刀角瓢虫卵的被捕食风险存在显著正相关关系。日本刀角瓢虫在4个番茄品种上的产卵选择性与日本刀角瓢虫对番茄叶片的附着力及番茄叶片上各类型叶毛密度均无显著相关性。番茄的7种叶毛类型其叶毛密度在4个番茄品种上都存在显著差异,除番茄Ⅰ型腺毛密度与日本刀角瓢虫的繁殖力(30 d内单雌产卵量)存在显著负相关关系外,其他6种类型的叶毛密度与日本刀角瓢虫子代表现及亲代表现均无显著相关性。日本刀角瓢虫雌成虫对4个番茄品种的气味无明显偏好。日本刀角瓢虫卵在4个番茄品种叶蝶和植株上的被捕食比例差异显著。【结论】日本刀角瓢虫雌成虫偏好在叶毛密度低的番茄品种叶片上产卵,番茄腺毛对日本刀角瓢虫成虫生命活动影响显著。     

QTLs for tomato powdery mildew resistance (Oidium lycopersici) in Lycopersicon parviflorum G1.1601 co-localize with two qualitative powdery mildew resistance genes

Tomato (Lycopersicon esculentum) is susceptible to the powdery mildew Oidium lycopersici, but several wild relatives such as Lycopersicon parviflorum G1.1601 are completely resistant. An F2 population from a cross of Lycopersicon esculentum cv. Moneymaker x Lycopersicon parviflorum G1.1601 was used to map the O. lycopersici resistance by using amplified fragment length polymorphism markers. The resistance was controlled by three quantitative trait loci (QTLs). Ol-qtl1 is on chromosome 6 in the same region as the Ol-1 locus, which is involved in a hypersensitive resistance response to O. lycopersici. Ol-qtl2 and Ol-qtl3 are located on chromosome 12, separated by 25 cM, in the vicinity of the Lv locus conferring resistance to another powdery mildew species, Leveillula taurica. The three QTLs, jointly explaining 68% of the phenotypic variation, were confirmed by testing F3 progenies. A set of polymerase chain reaction-based cleaved amplified polymorphic sequence and sequence characterized amplified region markers was generated for efficient monitoring of the target QTL genomic regions in marker assisted selection. The possible relationship between genes underlying major and partial resistance for tomato powdery mildew is discussed.     

Trichome‐based host plant resistance of Lycopersicon species and the biocontrol agent Mallada signata: are they compatible?

Trichome‐based host plant resistance of Lycopersicon (Solanaceae) species offers the potential to reduce pesticide use in tomato production, but its compatibility with biocontrol agents is largely unknown. The effect of trichome‐based host plant resistance on the lacewing biocontrol agent, Mallada signata, was assessed for five accessions of L. cheesmanii, four accessions of Lycopersicon hirsutum, two accessions of Lycopersicon pennellii, and one Lycopersicon esculentum cultivar. An intact leaf was isolated from the whole plant using Tangletrap to coat the petiole and 20 green peach aphids [Myzus persicae (Sulzer) (Homoptera: Aphididae)] were placed on the leaf surface. After 24 h, 10 lacewings were placed on the leaf. The numbers of dead, trapped by exudates, untrapped and predated lacewings and aphids, and the numbers that had left the leaf were recorded a further 24 h later. Differences in insect designations between accessions were analysed using ANOVA. A General Linear Model (GLM), consisting of the densities of each trichome type and leaf area, was fitted to the data to determine the role of trichomes on the observed effects on lacewings and aphids. Lacewing mortality was greater on one accession of L. pennellii and one accession of L. hirsutum than on L. esculentum. The GLM indicated that type IV trichomes decreased the numbers of aphids predated, and increased cannibalism and, along with type III trichomes, increased entrapment‐related predator mortality. Although there were no differences in the numbers of predated aphids, with the majority predated for all accessions, the compatibility of trichome‐based host plant resistance of Lycopersicon species and the biocontrol of aphids by lacewings is questionable.     

Most AAL toxin-sensitive Nicotiana species are resistant to the tomato fungal pathogen Alternaria alternata f. sp. lycopersici

The phytopathogenic fungus Alternaria alternata f. sp. lycopersici produces AAL toxins required to colonize susceptible tomato (Lycopersicon esculentum) plants. AAL toxins and fumonisins of the unrelated fungus Fusarium moniliforme are sphinganine-analog mycotoxins (SAMs), which are toxic for some plant species and mammalian cell lines. Insensitivity of tomato to SAMs is determined by the Alternaria stem canker gene 1 (Asc-1), and sensitivity is associated with a mutated Asc-1. We show that SAM-sensitive species occur at a low frequency in the Nicotiana genus and that candidate Asc-1 homologs are still present in those species. In Nicotiana spp., SAM-sensitivity and insensitivity also is mediated by a single codominant locus, suggesting that SAM-sensitive genotypes are host for A. alternata f. sp. lycopersici. Nicotiana umbratica plants homozygous for SAM-sensitivity are indeed susceptible to A. alternata f. sp. lycopersici. In contrast, SAM-sensitive genotypes of Nicotiana spegazzinii, Nicotiana acuminata var. acuminata, Nicotiana bonariensis, and Nicotiana langsdorffii are resistant to A. alternata f. sp. lycopersici infection concomitant with localized cell death. Additional (nonhost) resistance mechanisms to A. alternata f. sp. lycopersici that are not based on an insensitivity to SAMs are proposed to be present in Nicotiana species.